Phase equalizer useable in a LIND amplifier

Abstract

Apparatus for accomplishing phase equalization between two signal components derived from a common source includes circuitry for generating the sum and the difference of the two signal components and for deriving an error signal from the envelopes of the sum and difference. The error signal is mixed in a first mixer with the envelope of the sum signal and mixed in a second mixer with an envelope of an original signal from which the two input signal components to be phase equalized are derived. The output of the first mixer is applied to a phase adjuster which adjusts the phase of one signal component to be phase equalized so that desired phase equality is maintained between the two signal components. The output of the second mixer controls the gain of an amplifier which amplifies the envelope of the original input signal. A particular application of the invention is in a LIND (linear amplification using nonlinear devices) amplifier such as disclosed in U.S. Pat. No. 3,777,275 issued Dec. 4, 1973 to D. C. Cox.

What is claimed is: 
     
       1. Apparatus for equalizing the phase of two signal components originally derived from a common source, said components appearing in separate paths comprising: a combining device to which said two signal components to be phase equalized are applied and from which two outputs emanate, one output being the difference of said two signal components and the other output being the sum of said two signal components applied to said combining device;   first means for detecting the envelope of the difference output from said combining device;   second means for detecting the envelope of the summed output from said combining device;   a variable gain amplifier;   means for applying the envelope of a reference signal from which said two signal components are derived to said variable gain amplifier, the reference signal being derived from said common source;   means for summing the output of said variable gain amplifier and the envelope of the difference output to produce an instantaneous error signal;   a first means for correlating the instantaneous error signal with the envelope of the reference signal to produce a first signal;   means for applying the first signal to said variable gain amplifier to control the gain of said amplifier;   a second means for correlating the instantaneous error signal with the envelope of the summed output of said combining device to produce a second signal;   a phase shifter inserted in the path of one of said two signal components; and   means for applying the second signal to said phase shifter controlling the phase of the one of said two signal components.   
     
     
       2. Apparatus as described in claim 1 wherein said first means for correlating is a first mixer to which the instantaneous error signal and the envelope of the reference signal are applied and said second means for correlating is a second mixer to which the instantaneous error signal and the envelope of summed output of said combining device are applied. 
     
     
       3. Apparatus for equalizing the phase of two signal components as described in claim 1 wherein said apparatus further includes: means responsive to the instantaneous error signal and the envelope of the reference signal for controlling said phase shifter so as to shift the phase of one of said two signal components π radians.   
     
     
       4. Apparatus as described in claim 3 wherein said means responsive to the instantaneous error signal and the envelope of the reference signal includes: means for detecting the power level associated with the instantaneous error signal;   means for detecting the power level associated with the envelope of the reference signal; and   means for comparing the detected power levels, said means for comparing producing an output applied to said phase shifter to shift the phase of one of said two signal components by π radians when the difference between the detected power levels exceeds a predetermined level.   
     
     
       5. In combination, a component separator responsive to an input signal for producing two signal components and for producing an envelope of the input signal, a hybrid device for combining the two signal components to produce two output signals, a phase shifter inserted in the path of one of the two signal components between said component separator and said hybrid device, and means responsive to the two output signals and to the envelope of the input signal for controlling said phase shifter. 
     
     
       6. A linear amplifier of the type having a component separator for producing from an input signal two signal components and the envelope of said input signal, a combining device for combining said two signal components to produce two output signals one of which is a linearly amplified replica of said input signal, wherein the improvement comprises: a phase shifter inserted in the path of one of the two signal components between said component separator and said combining device; and   means responsive to the two ouput signals and to the envelope of the input signal for controlling said phase shifter.